- Tourette syndrome (criteria based on the TS Classification Study Group), which includes onset before 18 years, multiple involuntary motor tics, one or more vocal tics, a waxing and waning course, the gradual replacement of old symptoms with new ones, the presence of tics for more than one year, the absence of other medical explanations (effects of a substance (e.g., stimulants) or a general medical condition for tics, and observation of tics by a reliable examiner) or Chronic Motor Tic disorder (criteria similar to Tourette syndrome except for the absence of vocal tics)